Rotary drying drum



Jan. 16, 1968 lc s ET AL ROTARY DRYING DRUM 3 Sheets Sheet 1 Filed Nov.26', 1965 3%. 7 pm ALI Jan. 16, 1968 w, A, l s ET AL 3,363,328

ROTARY DRYING DRUM Filed Nov. 26, 1965 5 heets-Sheet 2 Jan. 16, 1968 w.A. DICKENS ET AL 3,363,328

ROTARY DRY ING DRUM Filed Nov. 26, 1965 3 Sheets-Sheet 5 United StatesPatent 3,363,328 ROTARY DRYING DRUM William A. Dickens and Sung Ho Hong,Neenah, Wis, a

signors to Kimberly-Clark Corporation, Neenah, Wis, a corporation ofDelaware Filed Nov. 26, 1965, Ser. No. 509,916 3 Claims. (Cl. 34-124)ABSTRACT OF THE DISCLGSURE A rotary drum for drying sheet materialadapted to have a condensible heating fluid supplied to it and having aseries of longitudinally extending grooves in its internal surface and apair of circumferential grooves in communication with and at the ends ofthe longitudinal grooves and having condensate removal pipes extendingoutwardly into said circumferential grooves for removing condensate frominside the drum.

The invention relates to rotatable drum constructions and moreparticularly to heated drier drums for drying paper webs and the like.

Paper is conventionally dried by means of hollow drums heated withcondensing steam and having the paper webs passing over the drums. Thesteam is supplied to the interior of such a drum at steam pressures upto 125 pounds per square inch which corresponds to a temperature of 353F., and a 12-foot diameter drier drum of this type supplied with thissteam pressure is suflicient for drying paper tissue at speeds of theorder of 3,000 feet per minute.

Obviously, relatively high strength drum constructions are needed inorder to withstand such steam pressures; and, if the steam temperatureis raised, for example to 450 F., in an attempt to provide higher dryingspeeds, the required steam pressure would be greater, such as about 400pounds per square inch for the 450 F. temperature, and these higherpressures necessitate still heavier drier drums with still thickershells. The thicker shells would have the effect of increasinglyimpeding the heat transfer to the sheet on the shells, and the heavierdrums would have higher initial costs. Therefore, the increases, if any,in drying speed would be relatively small, and the extra cost of suchheavy drums could not be expected to justify the small increases indrying speed obtainable.

It is an object of the present invention to provide an improved drierdrum and a system for supplying heating fluid to the drum by means ofwhich the relatively thin drums may be heated to higher temperaturesthan those obtainable using steam in the conventional manner; and, moreparticularly, it is an object to utilize fluid materials in such systemswhich have higher boiling points than that of water so as to accomplishthis result.

More particularly, it is an object of the invention to provide animproved drier drum of this type having a series of inwardly extendingribs on its inner periphery which will allow a direct contact betweenportions of the inner drum surface and the vapor of the heating fluidapplied to the drum but which will yet allow the condensed heating fluidto collect on the inner surface of the drum and to be drawn out of thedrier drum. It is contemplated that the ribs shall preferably extendlongitudinally of the drier drum, so that siphons or collecting pipesmay be provided at the ends of the drum to collect the condensed heatingfluid flowing between the ribs. The drum is rotatable and the siphons orcondensate collecting tubes may be either rotatable or stationary;however, the latter is preferred since the relative rotation between thesiphons and the drum may be utilized to provide a pumping effect to thecondensed heating fluid, propelling fit into and through the siphons forremoval from the rum.

The invention consists of the novel constructions, arrangements anddevices to be hereinafter described and claimed for carrying out theabove stated objects, and such other objects, as will be apparent fromthe following description of a preferred form of the invention,illustrated with reference to the accompanying drawings, wherein:

FIG. 1 is a fragmentary, longitudinal, sectional view of a drier drumincorporating the principles of the invention;

FIG. 2 is a diagrammatic illustration of a source of supply of heatedfluid for the drier drum;

FIG. 3 is a sectional view taken on line 33 of FIG. 1;

FIG. 4 is a sectional view taken on line 44 of FIG. 1;

FIG. 5 is a fragmentary view similar to FIG. 3 but on a further enlargedscale and of a small portion of the outer shell of the drier drum;

FIG. 6 is a longitudinal, sectional view of a portion of the outer shellof the drier drum; and

FIG. 7 is a view similar to FIG. 1 and showing a modified drier drum.

Like characters of reference designate like parts in the several views.

The drier drum and fluid supply system to the drum illustrated in theabove mentioned figures are preferably used with a fluid material whichhas a substantially higher boiling point than that of water and which isrelatively inert so as to eliminate corrosion problems with respect tothe drum. A material for example, that is satisfactory, is a low meltingpoint mixture of diphenyl and diphenyloxide. This material is acolorless, non-corrosive liquid and one form (commercially known asDowtherm E) has a condensing temperature of about 445 F. at 33.4 poundsper square inch (gauge pressure) and a latent heat of 107 B.t.u.s perpound. Another form of this material (known commercially as Dowtherm A)has a condensing temperature of about 450 F. at -7.7 pounds per squareinch and a latent heat of 129 B.t.u.s per pound. Used in the same drierdrum heating system to obtain the same drying eflect Dowtherm E could beoperated at 30 to 40 pounds per square inch within the drum whileDowtherm A would be operated at 7 pounds per square inch. Both of theseoperating pressures could be compared to the conventional operatingpressure for steam of pounds per square inch. Also, for purposes ofcomparison, steam at this pressure has a condensing temperature of 353F. and a latent heat of 868 B.t.u.s per pound. Dowtherm A and Dowtherm Eused under the above mentioned operating pressures of 30 to 40 poundsper square inch for Dowtherm E and 7 pounds per square inch for DowthermA would provide a heat flux through a certain drier drum of 25,500B.t.u.s per hour per square foot, while the steam at 125 pounds persquare inch in the same system would provide only 17,000 B.t.u.s perhour per square foot due to the lower temperatures of operation of thesteam.

Referring now to the drawings and in particular to FIGS. 1, 3, 4, 5 and6, the illustrated drier drum may be seen to comprise an outercylindrical shell 10 and end walls or heads 11 and 12. The end walls '11and 12 are respectively provided with longitudinally extending tubularend portions 13 and 14 by means of which the drum is rotatably mountedin bearings 15 and 16, the bearings being suitably mounted on pedestalsor other standards (not shown). The shell 10 and the heads 11 and 12 aresuitably fixed together as by conventional studs or screws (not shown).

A fixed hollow axle or shaft 17 extends through the drum and through theend portions '13 and 14 of the heads 11 and 12. Pressure seals 18 and 19are provided on the shaft 17 and within the head portions 13 and 14 forsealing the internal cavity 20 of the drum with re spect to the shaft17. Tubes 21 and 22 of insulating material are also provided within thehead portions 13 and 14 so as to insulate, to some extent, the seals 18and 19 with respect to high temperature fluid within the drum.

A plurality of vapor outlet tubes or nozzles 23 are fixed in the tubularshaft 17 and are directed into the cavity 20 for discharging vapor fromthe shaft 17 into the cavity 20. A vapor inlet port 24 is provided inthe shaft 17 for supplying heated vapor to the shaft and thereby to thecavity 20 through the tubes 23.

The shell on its internal peripheral surface is formed with a series ofribs 25 which are integral with the shell 10 and which are separated bygrooves 26. The ribs 25 and grooves 26 extend longitudinally of thedrier drum and shell 10 and terminate slightly short of attachment endflanges 10a and 10b of the shell 10, leaving internal peripheral grooves27 and 28 between the flanges 10a and 10b and the internal ribs 25.

A plurality of siphon pipes 29 are fixed with respect to and are carriedby the stationary tubular shaft -17, and the outer ends of these pipes29 extend into the grooves 27 and 28. As may be seen from FIG. 4, thepipes 29 are bent at right angles on their ends to have terminalportions 29a which lie approximately parallel with the adjacent internalsurface of the shell 10. The shell 10 rotates in the direction indicatedby the arow 30, and the terminal portions 29a of the pipes 29 extend inthe opposite direction from the direction of rotation of the shell.

A condensate collecting and discharge tube 31 extends through the centerof the hollow shaft 17, and each of the pipes 29 is connected to thetube 31. A support 32 is preferably provided for each of the siphonpipes 29, and the supports 32 are fixed with respect to the hollow shaft17 and with respect to the siphon pipes. The heads 11 and 12 arepreferably provided with radially extending fins 33 and 34 adjacent thepipes 29 and supports 32, as shown.

The source of heated fluid for the drier drum may comprise variousheating systems; however, for illustrative purposes, the system shown inFIG. 2 is suggested. The FIG. 2 system comprises a boiler 35 for heatingliquid which may utilize natural gas from a source 36. The boiler isconnected to the port 24 for the central shaft 17 by means of a conduit37. The tube 31 within the stationary hollow shaft '17. of the drierdrum is connected by means of a conduit 38 with a separating andreceiving tank 39, and the tank 39 is connected by means of a conduit 40with the boiler 35. A pump 41 is disposed in the conduit 40. Acompressor 42 is provided in a conduit 43 connecting the upper end ofthe tank 39 with the conduit 37, and the upper end of the tank 39 isalso connected by means of a conduit 44, which has a pump 45 therein,with a storage tank 46 for the heating liquid.

In operation, the heating fluid, which may be one of the Dowthermmixtures above mentioned, is heated in the boiler 35 and passes as avapor from the boiler through the conduit 37 to the central shaft 17 ofthe drier drum. The vapor is discharged through nozzles 23 from theshaft 17 into the cavity 20 of the drier drum, and the vapor heats theshell 10 of the drum and condenses in the drum. The condensate, alongwith some of the vapor, enters into the siphon pipes 29 and passesthrough them to the central tube 31 of the drum and passes through theconduit 38 to the separating and receiving tank 39. The compressor 42removes the vapor from the tank 39, which exists above a body 47 of thefluid in the bottom of the tank 39, and returns it into the conduit 37.The body of liquid 47 is maintained at a predetermined height within thetank 39 by automatic controlling means (not shown) which operates thepump 45 to pump fluid from the storage tank 46 into the tank 39 asneeded, and the pump 41 pumps the heating fluid in liquid form from thehot- 4 tom of the tank 39 through the conduit 40 to the boiler 35, asneeded, to maintain the desired supply of heated vapor to the drierdrum.

The paper sheet 48 (see FIG. 1) that is dried by the shell 10 issubstantially coextensive with the ribs 25 within the drum, and the drumis rotated to pass the sheet over it and dry the sheet. The heated vaporthat is discharged from the nozzles 23 into the cavity 20 of the drumheats the shell 10, and this heat is efiective on the web 48 for dryingthe web as the web passes over the shell 10 during rotation of the drierdrum. The vapor as it cools in heating the shell 1% condenses to a largeextent releasing its heat of condensation, and the condensate passeslongitudinally of the drum within the grooves 26 toward the peripheralgrooves 27 and 28 at the ends of the ribs 25. As will be observed fromFIG. 4, the ends 29a of the pipes 29 extend into directions opposite tothe direction of rotation of the drum indicated by the arrow 30; and,since the condensate moves with the shell -10 and the pipes 29 arestationary, the pipe ends 29a tend to scoop the condensate into them.Some of the vapor also passes into the pipes 29 and due to its pressureforces the condensate into the pipes 29, and this combination ofcondensate and vapor passes from the pipes 29 into the central tube 31for passage through the remainder of the system as above described.

It will be understood that the pressures of the heating fluid within thesystem may vary; however, as an example, the pressure within the boiler35 may be 50 pounds per square inch; the pressure within the cavity 20of the drier drum may be 30 pounds per square inch; and the pressure ofthe vapor within the tank 39 above the body of liquid 47 may be 10pounds per square inch.

Utilizing the high boiling point heat transfer liquids above mentionedto provide a high shell heating effect, it will be apparent,advantageously, that the vaporized liquid need be at or only slightlyabove atmospheric pressure in lieu of the high pressures that arenecessary using steam for a high heating effect; and, as a result, thedrum construction can be relatively light, since it does not need towithstand high pressures. Therefore, the tension stays commonly used insteam heated drier drums for papermaking, such as the stays 52 of thedrum shown and described in Malmstrom et al. Patent No. 3,099,543,issued July 30, 1963, need not be used while yet the drier drum may bemade with a relatively thin shell 10 providing relatively ready,unimpededheat transfer. Thus, utilizing the relatively light drier drum,using Dowtherm E, for example, operating pressures within the drum ofonly 30 to 40 pounds per square inch provide a much greater heatingeffect and paper drying effect than does steam at an operating pressureof pounds per square inch used with a relatively heavy drier drum of thetype shown in the above mentioned Malmstrom et al. patent. Utilizing theDowtherm, the system is capable of providing about a 50 percent increasein the heat flux per square foot through the drier shell as comparedwith steam, and this heat flux increase provides a substantial increasein the possible speed of drying for a paper web, such as a speedincrease of 600 to 1,000 feet per minute for a 7 /2 pounds per 2,880square foot paper sheet dried on a 12-foot diameter drier, for example.7

It is contemplated that the illustrated drier and supply system shall becapable of effective paper drying operation at high speeds, such asabove 5,000 feet per minute. At some high speeds of this generalmagnitude, the condensate flow within the drier drum becomes laminar innature, and the liquid heating medium in the form of condensate withinthe drier drum is an insulator. Therefore, the system for effectivelyand expeditiously removing condensate without allowing it to build up inthe drum has been provided, the system comprising the longitudinallyextending grooves 26 allowing condensate to flow longitudinally of thedrum to the peripheral grooves 27 and 28 in which the siphon pipes 29are effective for removing the condensate. As an important feature, the

system allows the inner surfaces of the ribs 25 to be in direct contactwith the heating fluid in its vapor form as supplied through the nozzles23, since condensate is mainly in the grooves 26 in the portion of theshell located beneath the sheet 48; and there thus exists a veryeffective heat transfer from the vapor to the shell 10.

The arrangement of the ribs 25 and the grooves 26 extendinglongitudinally of the drier drum, used with high boiling point liquidsuch as Dowtherm, not only provides higher heat fluxes through the shell10, due to the higher temperatures with which the Dowtherm may be usedas compared with those of steam and due to the relative thinness of theshell 10 attributable to the reduced pressures of operation, but the riband groove construction also provides a much improved temperatureuniformity in the shell. The heat transfer behavior of the condensate inthe grooves 26 is quite uniform inasmuch as the flow of condensate inthe grooves is practically laminar and its thickness and thicknessgradient from the center of each groove 26 to the ends of the groovesare very small at the high speeds of operation contemplated for thedrier drum. The high centrifugal force on the condensate within theshell 10 can be expected to maintain the condensate thickness in thegrooves 26 at not substantially more than 0.1 inch in the middle of theshell 10 and to maintain less than 0.04 inch difference in condensatethickness in the grooves 26 from the middle of the shell 10 to the endsof the ribs 25, due to the low viscosity of the Dow therm liquid at thetemperatures at which used. Temperature uniformity is also promotedinasmuch as the flow of condensate through the grooves 26 is undisturbedby the siphoning action of the siphon pipes 29, except at the end of thegrooves 26, which are outside the area or width of the sheet that isbeing dried.

Although the shell 10 may be formed of any suitable material, such ascopper-nickel alloy described in the patent to John F. Klement, No.2,937,965, it is contemplated that preferably the shell 10, as Well asthe heads 11 and 12, shall be made of cast iron of the conventionalcompositions now used for drier drums for paper machines, since verysatisfactory creping by creping blades for manufacturing creped tissuemay be obtained off of such cast iron shells. Although the dimensions ofthe ribs 25 and grooves 26 are not considered critical; as an example,the ribs 25 may have heights of 2 inches, and the ribs and the groovesmay have widths (peripherally of the shell 10) of about 1% inch. Thethickness of the shell 10 may, for example, be about 1% inch, measuredbetween the bottoms of the grooves 26 and the outer surface of the shell10. Due to the fact that lower pressures of operation are possible usingfluids of the type herein contemplated, cross stays for strengtheningthe drier are not needed; and, therefore, it is possible to use thestationary siphon pipes 29 cooperating with the ro tatable shell 10 andacting as a kind of centripetal pump for removing the condensate withinthe shell 19. Utilizing a heating fluid of this type having a lower heatof vaporization, the condensate formation Will be considerably greaterthan utilizing steam, and hence it is important that an eflicientcondensate removal system be provided, such as one of this type having apumping action. Since there is this pumping action, a minimum amount ofthe vapor of the heating fluid need be utilized for removing thecondensate out of the drier drum.

Although, as has been above explained, the invention is preferably usedwith relatively thin, unstayed drier drums, nevertheless, the inventionmay also be used with a stayed head drier of the type illustrated in theabove mentioned Malmstrom et al. patent, if desired. The drumillustrated in FIG. 7 is of the stayed type and comprises a centralhollow shaft 49 having end journals 50 for rotatably supporting thedrier in suitable bearings (not shown). The shaft 49 is provided with aplurality of outwardly directed, heating fluid discharge openings 51 init. The heating medium may be supplied to a port 52 at one end of theshaft 49, and a condensate withdrawal tube 53 may be disposed within andfixed with respect to the shaft 49 and may extend out of the shaft 49 atits other end.

The drum comprises a relatively thin cylindrical outer shell 54 rigidlysecured at its ends to relatively flat ringshaped heads 55 and 56 whichare fixed with respect to the hollow shaft Q9, so that the shell 54,heads 55 and 56 and the the shaft 49 all rotate together. The heads 55and 56 are provided with short, integral cylindrical sections 57 and 58,and a plurality of circumferentially spaced stays 59 connect thecylindrical sections 57 and 58.

The internal surface of the shell 54 is provided with ribs 25a. The ribs25a extend longitudinally of the drum and terminate short of the ends ofthe shell 54 so as to provide circumferential grooves 27a and 28aadjacent the ends of the shell. Siphon pipes 60 extend from the tube 53,outwardly through the shaft 49, and into the grooves 27a and 28a. Aplurality of the pipes 60 are provided for each of the circumferentialgrooves 27a and 28a, and these pipes are circumferentially spaced withinthe drum and extend between the stays 59.

Heating fluid in the form of vapor is supplied to the port 52 for thepurpose of heating the drum, and it flows through the openings 51 intothe internal cavity 61 within the drum. The heating fluid condenseswithin the cavity 61 and heats the outer shell 54 particularly by directcontact of the heating fluid vapor with the ribs 25a in the same manneras the heating fluid is effective for heating the shell 10 in the firstembodiment. Condensed heating fluid flows between the ribs 25::longitudinally of the drum to each of the circumferential grooves 27aand 28a in which it collects. Due to the pressure of the heating fluidwithin the cavity 61, which is higher than the pressure maintained inthe tube 53, some heating fluid in vapor form flows into the pipes 60and at the same time draws condensed heating fluid into these pipes outof the circumferential grooves 27a and 23a, and the condensed heatingfluid flows from the pipes 60 into the tube 53 for return to the systemfor heating the fluid.

We wish it to be understood that the invention is not to be limited tothe specific constructions and arrangements shown and described, exceptonly insofar as the claims may be so limited, as it will be understoodto those skilled in the art that changes may be made without departingfrom the principles of the invention. In particular, it will beunderstood that although we have described the ribs 25 and 25a as beinglongitudinal with respect to the drier drums and shells l0 and 54, theribs can instead be formed slightly helically within the shells, suchthat the grooves between the ribs are not substantially increased inlength and are thus substantially longitudinal; and we consider that theribs 25 and 25a should be helically inclined no more than for an angleof 25 with respect to the longitudinal center of the drum for them to beconsidered substantially longitudinal. Also, it will be understood that,although we have described the drum for use in connection with thedrying of paper, the drum also can be used for drying any other sheetmaterial.

What is claimed is:

1. Drying mechanism for sheet material comprising a hollow shell closedon its ends and rotatably mounted, said shell being provided withalternate ribs and grooves on its inner surface which extendlongitudinally of the shell, said grooves being of substantiallyuniform. depth for their complete length, said ribs being discontinuousadjacent the ends of the shell so as to provide circumferential groovesdisposed on both ends of said shell in communication with saidlongitudinal grooves, means for supplying a condensible heating fluidinto said shell, and means for withdrawing condensate from the shell andin cluding a pipe extending into each of said circumferential grooveswhereby condensate may flow through each of said longitudinal groovesfrom the center of each 7 groove to its opposite ends and into saidcircumferential grooves and may flow from the latter through said pipes.

2. Drying mechanism according to claim 1, said condensate withdrawingmeans including a stationary tube than that of water and conduit meansfor connecting said source with said hollow shell.

References Cited extending longitudinally through said shell and saidpipes 5 UNITED STATES PATENTS being connected with said tube and beingstationary, each 971,176 9/ 1910 Dexter 34-119 of said pipes on its endWithin one of said circumferential gultchins 34-125 u ton 34 -124grooves hav ng a portion extending opposite to the direc- 2,413,56712/1946 H mb stel 3 124 ion of rotation of said shell so that the pipesact to scoop 10 3 099 543 7/1963 Malmstrom et 31 34-124 condensate fromthe circumferential grooves into the pipes 3:217:426 11/1965 Barnscheidtet X as the condensate travels along with said shell. 3,224,110 12/1965Kroon 34 124 3. Drying mechanism according to claim 1, said heatingfluid supplying means including a source of a heated 1 fluid of a typehaving a substantially higher boiling point 5 FREDERICK L. MATTESON,IR., Primary Examiner.

A. D. HERRMANN, Assistant Examiner.

